Data is collected from women diagnosed with primary breast cancer at 3 points (5 visits): (i) after breast cancer surgery, but before chemotherapy begins (2 visits to NIH day hospital 1 week apart); (ii) 2-3 weeks after chemotherapy has ended (2 visits, 1 week apart); and (iii) 6 months after chemotherapy has ended (1 visit). Tests conducted during these visits include evaluation of blood for hormones, growth factors, and leptin; body composition by DXA; visceral and subcutaneous abdominal adipose tissue by an axial CT scan; and evaluation of resting metabolic rate and daily energy expenditure by a single administration of doubly labeled water at visits "a" and "b" during data collection timepoints 1 and 2. Questionnaires assessing epidemiologic risk factors for breast cancer, dietary intake, physical activity, depression, and quality of life are also administered at the three timepoints.